The present invention relates to intraocular lenses (IOLs). More particularly, the present invention relates to IOLs that provide accommodating movement in the eye.
The human visual system includes the eyes, the extraocular muscles which control eye position within the eye socket, the optic and other nerves that connect the eyes to the brain, and particular areas of the brain that are in neural communication with the eyes. The visual system is particularly well adapted for the rapid and precise extraction of spatial information from a field of view which is accomplished by analyzing the continuously changing patterns of radiant flux impinging upon the surfaces of the eyes.
Image formation is greatly complicated by the movement of the eyes within the head, as well as by the movement of both eyes and the head relative to the external sea of radiant energy. Visual input is ordinarily sampled by discrete momentary pauses of the eyes called fixations, interrupted by very rapid ballistic motions known as saccades which bring the eye from one fixation position to the next. Smooth movements of the eyes can occur when an object having a predictable motion is available to be followed.
Each eye forms an image upon a vast array of light sensitive photoreceptors of the retina. The cornea is the primary refracting surface which admits light through the anterior part of the outer surface of the eye. The iris contains muscles which alter the size of the entrance port of the eye, or pupil. The crystalline lens has a variable shape, under the indirect control of the ciliary muscle. Having a refractive index higher than the surrounding media, the crystalline lens gives the eye a variable focal length, allowing accommodation to objects at varying distances from the eye.
Much of the remainder of the eye is filled with fluids and materials under pressure which help the eye maintain its shape. For example, the aqueous humor fills the anterior chamber between the cornea and the iris, and the vitreous humor fills the majority of the volume of the eye in the vitreous chamber. The crystalline lens is contained within a third chamber of the eye, the posterior chamber, which is positioned between the anterior and vitreous chambers.
The human eye is susceptible to a score or more of disorders and diseases, a number of which attack the crystalline lens. For example, cataracts mar vision through cloudy or opaque discoloration of the lens of the eye. Cataracts often result in partial or complete blindness. If this is the case, the crystalline lens can be removed and replaced with an intraocular lens, or IOL.
While restoring vision, conventional IOLs have limited ability for accommodation (i.e., the focusing on near objects). This condition is known as presbyopia. To overcome presbyopia of an IOL, a patient may be prescribed eyeglasses. Alternative attempts in the art to overcome presbyopia focus on providing IOLs with accommodation ability. Accommodation may be accomplished by either changing the shape of the IOL, e.g., to become more convex to focus on near objects, or by moving the IOL along its optical axis. For example, a number of these approaches bias an IOL to be located in the most posterior position of the posterior chamber of the eye under rest conditions. When near focus is required, the ciliary muscle contracts, and the IOL moves forwardly, which is known as positive accommodation. In the absence of ciliary muscle contraction, the IOL is biased rearwardly to the most posterior position. While these approaches may provide limited accommodation, the posterior bias and the configuration of the IOL prevent sufficient forward axial movement required for full-range accommodation.
In view of the foregoing, it would be beneficial in the art to provide IOLs adapted for sufficient accommodation to reduce significantly or to overcome the effects of presbyopia.
The present invention provides new and enhanced intraocular lenses (IOLs). The present IOLs enhance accommodation of an optic. More specifically, the IOLs of the present invention enhance accommodation by converting radial movement of the capsular bag to axial movement of an optic. In addition, the present IOLs may also amplify such radial movement to effect a greater degree of positive accommodation for near vision.
According to one aspect of the present invention, an intraocular lens includes an optic and a movement assembly. The optic is adapted to focus light onto a retina of an eye. The movement assembly is adapted to cooperate with the eye to effect accommodating movement of the optic along an optical axis thereof. The movement assembly includes at least one, and preferably a plurality of, movement members and a suspension structure. The movement members are coupled to a periphery of the optic. The suspension structure is coupled to the movement members and is adapted to be in contact with a peripheral region of a capsular bag of an eye. The movement members are adapted to convert radial movement of the suspension structure caused by movement of the capsular bag to axial movement of the optic.
One of the advantages of the present invention is that the movement members may be adapted to amplify the radial movement of the suspension structure. Accordingly, substantial positive accommodation for near vision is possible with a relatively small contraction of the capsular bag. For example, according to one preferred embodiment of the invention, the movement members are configured to increase or amplify radial movement of the suspension structure into axial movement of the optic by approximately 200%.
According to another aspect of the IOL of the present invention, the movement members are articulated. For example, each of the movement members may include a first segment and a second segment pivotally coupled together. A distal end of the first segment is pivotally coupled to the suspension structure, and a proximal end of the second segment is pivotally coupled to a periphery of the optic.
This articulated two-segment linkage arrangement of the movement members allows radial movement to be converted and amplified into axial movement. More specifically, radial forces directed inwardly during contraction of the capsular bag are carried by the first segment. These forces are then transferred to the second segment at a pivot disposed between the two segments. The first segment and, correspondingly, the optic are urged anteriorly. This motion is amplified as the capsular bag continues to contract as the pivot follows a curved path which is translated into substantially axial movement of the optic.
According to another aspect of the invention, the suspension structure may include a plurality of arcuate contact plates each coupled to a respective one of the movement members. The arcuate contact plates are configured to support the IOL within the capsular bag. One of the advantages of this embodiment of the present invention is that the IOL is vigorously held within the capsular bag. More specifically, the contact plates collectively have a relatively large contact surface which engages with and supports the capsular bag.
The relatively large surface area of the contact plates may also promote cellular and fibrous growth to this portion of the IOL, which further holds and retains the IOL within the capsular bag. Post-operative cellular and fibrous growth of the interior of the capsular bag to the contact plates is facilitated by the vigorous contact of the contact surface with the capsular bag.
In addition to promoting desired post-operative fibrous growth, the IOL of the present invention inhibits unwanted posterior capsule opacification (PCO) onto the optic. To do so, the movement assembly may include a plurality of sharp discontinuities between the contact plates and the optic. Accordingly, cellular growth from the capsular bag to the optic is inhibited.
According to another aspect of the IOL of the invention, the suspension structure may include a fulcrum ring coupled to the movement members, thereby interconnecting the movement members. The first segment of each movement member rotates about the fulcrum ring during accommodation.
Any and all of the features described herein and combinations of such features are included within the scope of the present invention provided that the features of any such combination are not mutually inconsistent.